Variables in early discrimination learning. III. Simultaneous vs. successive stimulus presentation.

Abstract

In a previous study in this series it was found that children had great difficulty discriminating between tones of different pitch (4)- It was shown that at least part of the difficulty was due to the response required of S. Another condition of particular concern for the present experiment was that of the method of stimulus presentation; the stimuli were presented successively, a response being required to each stimulus. A number of studies have contrasted simultaneous and successive methods of stimulus presentation in the study of discrimination learning, and a variety of results have been obtained (I, 2, 5, 6). The various procedural differences, as well as stimulus and subject differences, make the interpretation of these results difficult. Inasmuch as Loess and Duncan (5) obtained a difference in learning speed between simultaneous and successive conditions with adult Ss when the discrimination was a difficult one, it seemed likely that such a difference would also be found with children. If it could be established that children do find the successive presentation condition more difficult, this would provide the opportunity for studying some of the factors that might be responsible for the difference in difficulty. The stimulus presentation conditions as used by Loess and Duncan were essentially as follows: when the stimuli were presented simultaneously, S was required to approach one or the other stimulus, regardless of its position to the right or left, in order to receive reinforcement. When the stimuli were presented successively, a single stimulus at a time, a different response was required for each stimulus. Thus, this latter condition not only provided less opportunity for comparison of the stimuli but also called for a different type of response from S. Therefore, the present study was designed to test the hypothesis that discrimination learning with successive presentation of the stimuli is more difficult than when the stimuli are presented simultaneously and that this difficulty can be at least partially accounted for in terms of the response called for under the successive presentation condition.